Traction control, when activated, can override a driver's torque request and instead operates the engine at a reduced torque output and/or increases wheel braking to reduce wheel spin. The reduced wheel spin, or slip, can increase the traction between the wheels and road surface to enable a vehicle to negotiate low friction surfaces. Such an approach relies on the premise that reducing wheel slip generates increased traction.
However on a surface with a high friction coefficient (μ) (e.g., a race track or a demonstration surface), higher wheel slip speeds, under specific circumstances, may provide improved acceleration and performance. This can be especially true when a driver performs various low speed demonstrations and/or wants to test the limits of performance on a closed track. Thus, in such situations, the driver can manually deactivate traction control completely in order to generate the wheel spin during an acceleration event, for example.
The inventors herein have recognized a problem with such an approach. In particular, many drivers do not have the skill to achieve and control a desired amount of wheel slip. Further still, even if the driver can generate a desired level of slip when accelerating from rest with traction control disabled, it can be difficult for the driver to control the decrease of slip as the vehicle accelerates to actually achieve any improvement in vehicle acceleration, as compared with an acceleration having little or no slip. Likewise, it can be equally difficult for the operator to manually engage traction control during the wheel spin event to obtain a controlled transition to non-slipping conditions during the vehicle launch.